1. Field of the Invention
The present invention relates to a rotary motion type one-way clutch adapted to be used for a motor-cycle, a snow mobile or the like, which exhibits a one-way clutch function at a rotational speed not less than a predetermined speed.
2. Related Background Art
In general, a one-way clutch is composed of an outer race and an inner race which are rotated, relative to each other, a sprag or a roller for transmitting a torque between the inner race and the outer race, which is meshed with a cam surface formed on a raceway surface of the inner race or the outer race so as to transmit torque in only one direction. Further, the one-way clutch slips in a reverse direction.
Among one-way clutches as mentioned above, there has been known the one in which a roller received in a pocket (recess) formed in either the inner race or the outer race is locked from rotation through such a wedging action that the roller is engaged with a wedge part formed on the outer periphery of the inner race, depending upon a direction of rotation thereof.
For example, Japanese Patent Application No. 2003-344618 discloses such a configuration that a roller and a weight element are accommodated in a recess formed in the inner race, and the roller is locked under wedge action in the clockwise rotation of an outer race, being pressed by the weight element under centrifugal action, in order to lock the outer race from rotating, relative to the inner race.
In the Japanese Patent Application No. 2003-344618, the inner race is formed at its outer periphery with a plurality of recesses, having a bearing surface and a weight element operating surface for the outer race, in parts of the outer periphery of the inner race.
However, the configuration disclosed in the Japanese Patent Application No. 2003-344618 inevitably causes the shape of the inner race to be complicated since the inner race is formed with both bearing surface and weight element operating surface. Further, since the bearing surface is made of one and the same material as that of the inner race, the specification required for a bearing have not always been satisfied.